1. Field of the Invention
The present invention relates to an external light blocking film, a method of fabricating the same and a filter having the same. Particularly, the present invention relates to an external light blocking film which can improve a Bright Room Contrast Ratio (BRCR), luminance and viewing angle and can be easily fabricated to save the fabrication time and cost.
2. Description of the Related Art
Display devices include televisions, monitors of personal computers, portable display devices, and so on. Display devices are recently getting larger sized and thinner.
Accordingly, flat panel display (FPD) devices such as plasma display panel (PDP) devices, liquid crystal display (LCD) devices, field emission display (FED) devices, and organic light emitting display (OLED) devices take the place of cathode ray tube (CRT) device, which was representative of display devices.
Hereinafter, PDP devices and a filter therefor will be exemplified but the present invention is not limited thereto. For example, a filter according to the present invention can be used for large sized display devices such as OLED devices, LCD devices and FED devices; small sized display devices such as Personal Digital Assistance (PDA) devices, display devices for small sized games, display devices for small mobile phones; and flexible display devices.
Especially, a PDP device is in the limelight since it has excellent display characteristics such as high luminance, a high contrast ratio, low after-image, and a wide viewing angle.
A PDP device causes gas discharge between electrodes by applying a direct or alternating voltage to the electrodes, then a fluorescent material is irradiated with ultraviolet rays caused by the gas discharge to be activated, and thereby light is generated. A PDP device displays images by using the generated light.
However, a PDP device has drawbacks that a large amount of electromagnetic waves and near infrared rays is emitted due to its intrinsic characteristics. The electromagnetic waves and near infrared rays emitted from a PDP device may have a harmful effect to the human body, and cause malfunction of precision appliances such as a cellular phone and a remote controller. Further, a PDP device has a high surface reflection and has lower color purity than a CRT device due to orange color light emitted from gas such as He or Xe.
Therefore, a PDP device employs a PDP filter in order to block electromagnetic waves and near infrared rays, reduce light reflection, and improve color purity. The PDP filter is installed in front of a panel assembly. The PDP filter is generally fabricated by adhering or bonding together a plurality of functional layers such as an electromagnetic shielding layer, etc.
In addition, in order to improve a Bright Room Contrast Ratio and luminance, the PDP filter includes an external light blocking film to block external light entering from the outside and absorb external light reflected by the panel assembly.
The external light blocking film includes a micro pattern in the shape of stripes. The external light blocking film causes a moiré pattern due to interference with a stripe pattern of boundaries between cells of the panel assembly, when installed in front of the panel assembly. Image quality deteriorates due to the moiré pattern caused by interference between a shadow created when the external light blocking film having the micro pattern is exposed to external light and the stripe pattern of the panel assembly.
Since it is impossible to remove the stripe pattern of the panel assembly, in order to remove the moiré pattern, a pitch of the stripes of the external light blocking film should be much smaller or larger than a pitch of the stripes of the panel assembly or the stripes of the external light blocking film should be inclined at some angle.
However, if the pitch of the stripes of the external light blocking film increases, an ability to block external light decreases. In addition, it is difficult to fabricate the external light blocking film with a narrow pitch stripe pattern. On the other hand, the inclined stripes lower an ability to block external light and increase consumption of a film.
One of major problems in fabricating the external light blocking film is to prepare a template. A machined template of metal is usually used to form a micro pattern. However, a machining process of fabricating the metal template has a problem in that the fabrication cost is high and the fabrication time is long. In addition, the machined metal template can form only a simple pattern such as a stripe pattern. In addition, the conventional external light blocking film has a problem in that the stripe pattern thereof causes the moiré pattern to make image quality worse, as mentioned above.